How to do custom Freestyle brush shape in Blender 2.74?
Have you looked into example .blend files for using textured strokes?  If not, try a couple of example .blend files available within the Blender 2.71 release log you cited, i.e.:


http://wiki.blender.org/index.php/File:Teapot_pencil.blend


http://wiki.blender.org/index.php/File:Mouse.Blend

Start from one of these existing line styles for textured strokes, and customize it with your texture PNG image.

EDIT: In reply to the updated question (22 May 2015)

Freestyle textured strokes always use a texture image as non-overlapping tiles repeated along stroke.  Internally, textured strokes in Freestyle are rendered using UV texture mapping (that is a general functionality of Blender).  Freestyle strokes have its own UV coordinates along stroke to map a 2D point in a texture image on to another point in the 2D stroke space.  This means that the texture image cannot be mapped in such a way that one tile overlaps on top of another.  (I guess this is a general limitation of UV texture mapping.)

I believe you need to rely on other Freestyle options to achieve what you are intended to do.  How about using the Calligraphy thickness modifier instead?